You can download trial versions for free from Adobe, so I suggest you do that and try them. Lightroom and Photoshop work in different ways, they're not exactly replacements for each other so you may still need both depending on what level of editing you want to do.

Personally I don't have any need for Lightroom (too slow, limited editing functionality), and Elements does 99% of my editing needs. The full PS would likely provide that missing 1% and then some, but without the student discount I don't think it is worth it for me.